#include <stdio.h>
#include <string.h>
#include "dbg.h"

int normal_copy(char *from, char *to, int count)
{
	int i = 0;

	for(i = 0; i < count; i++) {
		to[i] = from[i];
	}

	return i;
}

int duffs_device(char *from, char *to, int count)
{
	int n = (count + 7) / 8;

	switch(count % 8)  {
		case 0: do { *to++ = *from++;
		case 7: *to++ = *from++;
		case 6: *to++ = *from++;
		case 5: *to++ = *from++;
		case 4: *to++ = *from++;
		case 3: *to++ = *from++;
		case 2: *to++ = *from++;
		case 1: *to++ = *from++;

		} while(--n > 0);
	}

	return count;
}

int zeds_device(char *from, char *to, int count)
{
	int n = (count + 7) / 8;

	switch(count % 8) {
		case 0:
		again: *to++ = *from++;

		case 7: *to++ = *from++;
		case 6: *to++ = *from++;
		case 5: *to++ = *from++;
		case 4: *to++ = *from++;
		case 3: *to++ = *from++;
		case 2: *to++ = *from++;
		case 1: *to++ = *from++;
				if(--n > 0) goto again;
	}

	return count;
}

int valid_copy(char *data, int count, char expects)
{
	int i = 0;

	for(i = 0; i < count; i++) {
		if(data[i] != expects) {
			log_err("[%d] %c != %c", i, data[i], expects);
			return 0;
		}
	}

	return 1;
}

int main(int argc, char *argv[])
{
	char from[1000] = {'a'};
	char to[1000] = {'c'};
	int rc = 0;

	// set up the from to have some stuff
	memset(from, 'x', 1000);
	// set it to a failure mode
	memset(to, 'y', 1000);
	check(valid_copy(to, 1000, 'y'), "Not initialized right.");

	// use normal copy
	rc = normal_copy(from, to, 1000);
	check(rc == 1000, "Normal copy failed: %d", rc);
	check(valid_copy(to, 1000, 'x'), "Normal copy failed.");

	memset(to, 'y', 1000) ;

	// duffs version
	rc = duffs_device(from, to, 1000);
	check(rc == 1000, "Duff's device failed: %d", rc);
	check(valid_copy(to, 1000, 'x'), "Duff's device failed copy.");

	// reset
	memset(to, 'y', 1000);

	// my version
	rc = zeds_device(from, to, 1000);
	check(rc == 1000, "Zed's device failed: %d", rc);
	check(valid_copy(to, 1000, 'x'), "Zed's device failed copy.");

	return 0;
error:
	return 1;
}
